My days at the laboratory bench are over, but having a baby presented me with a prime opportunity to get back into the science game.

Even before Baby V arrived, I was already messing with the poor girl. When I was pregnant, I would hold really still, then suddenly bend my knees to see if I could make her Moro, the startle reflex in which the baby suddenly flings her arms out wide and then slowly, slowly brings them in like jazz hands. (My mom calls this the tree-hugger reflex: If a baby’s plum...